Scheduler Supporting Web Service Invocation

ABSTRACT

The present invention proposes a method and a corresponding system for scheduling invocation of web services from a central point of control. A scheduler accesses a workload database, which associates an execution agent and a descriptor with each submitted job. The descriptor identifies a desired web service, an address of a corresponding WSDL document, and the actual content of a request message to be passed to the web service. Whenever the job is submitted for execution, the scheduler sends the job&#39;s descriptor to the associated agent. In response thereto, the agent downloads the WSDL document that specifies the structure of the messages supported by the web service. The scheduler builds a request message for the web service embedding the desired content into the structure specified in the WSDL document. The agent sends the request message to an endpoint implementing the web service, so as to cause its invocation.

TECHNICAL FIELD

The present invention relates to the data processing field, and morespecifically to a scheduling method and a corresponding system.

BACKGROUND ART

Scheduling methods are commonly used in a data processing system forcontrolling submission of different work units (for example, jobs in abatch processing). For this purpose, several types of schedulers havebeen proposed in the last years to automate the submission of largequantities of jobs. An example of scheduler is the “Tivoli WorkloadScheduler” by IBM Corporation.

A scheduler submits the jobs according to a predefined plan, whichestablishes a desired flow of execution of the jobs. Whenever a job mustbe submitted, the scheduler dispatches an execution request to acorresponding agent; the agent directly controls the execution of thejob and returns feedback information to the scheduler. In this way, thescheduler provides a single central point of control for all the jobs.

Moreover, most of the available schedulers offer additional services.Typically, the schedulers are very sophisticated in handling temporaland predecessor constraints (for example, defined by the completion ofother jobs or by the availability of system resources). The schedulerscan also be provided with a Graphical User Interface (GUI), which allowscreating, modifying and deleting the definition of the jobs or plans,and which allows controlling and monitoring the operations performed bythe scheduler. Moreover, some schedulers integrate performancemonitoring, load balancing and/or reporting functions.

A drawback of the schedulers known in the art is that they arespecifically designed for working in a close environment within acompany. Indeed, the schedulers typically submit the work units forexecution on a single computer (wherein the scheduler itself isrunning), or at most support the managing of a cluster of computersbeing connected through a private network of the company.

In any case, no scheduler known in the art can be used in an openenvironment to control the invocation of external services (typicallyprovided by third parties). Indeed, the external services can beaccesses in a number of ways, which are generally incompatible with therequirements of the scheduler.

This problem has been exacerbated by the widespread diffusion of theINTERNET, and particularly of web services. A web service (also calledapplication service) consists of a collection of functions that can beexploited by other applications through an interface defined in astandardized way (irrespective of the actual implementation of theoffered functions). The web services are accessed via ubiquitousprotocols and data formats (such as the HTTP, SOAP and XML). In thisway, the web services have become the standard platform for applicationintegration, being the fundamental building blocks in the move todistributed computing on the INTERNET.

Therefore, the limitations of the available schedulers strongly hindersthe full exploitation of the INTERNET; particularly, this impairs theinteroperability of legacy applications with web services provided bythird parties (for example, when implementing online transactions ine-commerce applications).

SUMMARY OF THE INVENTION

It is an object of the present invention to enable a scheduler to manageexternal services.

Particularly, it is an object of the present invention to allow thescheduler to invoke the external services.

It is another object of the present invention to provide a schedulingmethod that can be used in heterogeneous environments.

It is yet another object of the present invention to support theintegration of the scheduler with the external services.

Particularly, it is an object of the present invention to exploit theadditional functions already available in the scheduler for managing theexternal services.

The accomplishment of these and other related objects is achieved by amethod of scheduling execution of work units in a data processinginfrastructure with a distributed architecture, the method including thesteps under the control of a central scheduling application of:associating at least one of the work units with a descriptor includingan indication of an external service being accessible according to apredefined interface document, submitting the work units for executionaccording to a predefined plan, retrieving the interface document ofeach external service associated with the submitted work units, buildinga request message for each external service associated with thesubmitted work units according to the corresponding interface document,and sending each request message to the corresponding external serviceto cause the invocation of the external service.

The present invention also provides a computer program for performingthe method and a product embodying the program. A corresponding systemfor scheduling execution of work units and a data processinginfrastructure including the system are also encompassed.

The novel features believed to be characteristic of this invention areset forth in the appended claims. The invention itself, however, as wellas these and other related objects and advantages thereof, will be bestunderstood by reference to the following detailed description to be readin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a schematic block diagram of a data processinginfrastructure in which the method of the invention is applicable;

FIG. 1 b shows the functional blocks of a generic computer of theinfrastructure;

FIG. 2 depicts the main software components that can be used forpracticing the method;

FIGS. 3 a-3 c show a diagram describing the flow of activities relatingto an illustrative implementation of the method.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

With reference in particular to FIG. 1 a, a schematic block diagram of adata processing infrastructure 100 with a distributed architecture isillustrated. The infrastructure 100 includes a central scheduling server105, which is used to submit non-interactive jobs. The scheduling server105 communicates with multiple servers 110 controlling the actualexecution of the jobs. One or more of the execution servers 110 accessesa global network 115, typically consisting of the INTERNET. As aconsequence, these execution servers 110 can interact with multiple webservers 120 providing corresponding services (for example, implementingstorage or customer relationship management). The web services madeavailable in the INTERNET 115 are listed in a distributed registry,which is implemented by a set of corresponding servers 125.

More in detail, the distributed registry consists of an XML-baseddocument conforming to the UDDI (Universal Description, Discovery andIntegration) specification. The web services provided by each businessorganization are specified in a WSDL (Web Services Description Language)document. The WSDL document consists of a set of XML-based definitions,which are split into abstract definitions and concrete definitions (soas to allow reusing the abstract definitions for differenttechnologies). Particularly, the abstract definitions are comprised oftypes (specifying data types relevant for the web services), messages(specifying the types of data being exchanged), operations (specifyingsupported actions in terms of the messages involved), and portType(grouping related operations). On the other hand, the concretedefinitions are comprised of bindings (associating concrete protocol anddata format specification to operations and messages for the portTypes),ports (specifying network addresses for the web servers implementing theportTypes) and services (grouping related ports). Moreover, the WSDLspecification supports extendibility elements, which can be used toprovide information specific for particular technologies (either in theabstract definitions or in the concrete definitions).

The definitions of the WSDL document are enclosed within the followingelement:

<definitions name=myName targetNamespace=myNamespace>     ....<\definitions>

The attributes “name” and “targetNamespace” can be optionally used toidentify the WSDL document in a lightweight form. Particularly, theattribute “name” provides the name assigned to the WSDL document(“myName”), and the attribute “targetNamespace” specifies acorresponding namespace (“myNamespace”). The namespace consists of aunique identifier that is used to qualify the name; the namespace iscommonly given the URI (Uniform Resource Identifier) of a desired webpoint of content (for example, a web site address).

The types are defined by the following statement:

<types>     <schema targetNamespace=mySchema>       ....     </schema></types>

The tag “schema” can be used to specify the URI of a desired schema(“mySchema”); the schema provides an abstract representation of the datatypes according to the XSD (XML Schema Definition) specification.Alternatively, specific data types can be added via extensibilityelements (providing an XML container for the type definitions).Preferably, basic data types are defined with the following form:

<element name=myElement type=myType/>

wherein the attribute “name” provides a unique name of the data typewithin the WSDL document (“myElement”) and the attribute “type”references the desired data type. Conversely, complex data types aredefined combining multiple data types with the following form:

<element name=myElement>     <complexType>       <all>         ....      </all>     </complexType> </element>

Each message consists of one or more parts, which represent its logicalcomponents:

<message name=myMessage>     <part name=myPart element=myElementtype=myType/>     .... </message>

The attribute “name” of the message provides a unique name within theWSDL document (“myMessage”). For each message part, the attribute “name”defines a unique name within the message (“myPart”); the message partincludes one or more parameters, each one consisting of an attribute“element”, specifying the name of the parameter (“myElement”), and anattribute “type”, referencing its type (“myType”).

The definition of each portType (with the corresponding operations) hasthe following syntax:

<portType name=myPortType>   <operation name=myOperation>     <....name=myMessage message=myDefinition/>   </operation>   .... </portType>

The attribute “name” of the portType provides a unique name within theWSDL document (“myPortType”). For each operation, the attribute “name”defines a unique name within the portType (“myoperation”). The operationconsists of one or more messages (qualified by a corresponding element,as described in the following); each message is defined by an attribute“name”, specifying the name of the message (“myMessage”), and anattribute “message”, referencing its abstract definition(“myDefinition”). In addition, a further attribute “parameterOrder” maybe used to specify an actual signature of the operation (via an orderedlist of its parameters).

The WSDL supports four operation types: one-way (wherein a message isreceived only), request-response (wherein a message is sent and acorrelated message is received), solicit-response (wherein a message isreceived and a correlated message is sent), and notification (wherein amessage is received only). The one-way operation:

<operation name=myOperation>   <input name=myInputmessage=myInputDefinition/> </operation>includes an element “input” for the request.

The request-response operation:

<operation name=myOperation>   <input name=myInputmessage=myInputDefinition/>   <output name=myOutputmessage=myOutputDefinition/>   <fault name=myFaultmessage=myFaultDefinition/> </operation>includes an element “input” for the request, an element “output” for theresponse, and an element “fault” for any error that may be returned as aresult of the operation.

Similar messages are included in the solicit-response operation:

<operation name=myOperation>   <output name=myOutputmessage=myOutputDefinition/>   <input name=myInputmessage=myInputDefinition/>   <fault name=myFaultmessage=myFaultDefinition/> </operation>and in the notification operation:

<operation name=myOperation>   <output name=myOutputmessage=myOutputDefinition/> </operation>

In order to avoid having to name each message within an operation, theWSDL provides some default values. Particularly, if the attribute “name”is not specified for the single message of a one-way or notificationoperation, the name of the message defaults to the one of the operation;likewise, if the elements “name” are not specified for the input/outputmessages of a request-response or solicit-response operation, the namesof the messages default to the one of the operation with“request”/“solicit” or “response” appended, respectively.

The binding of each portType is provided by the following element:

<binding name=myBinding type=myPortType>   ....   <operationname=myOperation>     ....     <input name=myInput>       ....    </input>     <output name=myOutput>       .....     </output>    <fault name=myFault>       ....     </fault>   </operation></binding>

The attribute “name” provides a unique name for the binding within theWSDL document (“myBinding”); the attribute “type” references theportType that is bound (“myPortType”). Extendibility elements are usedto add further information on the binding and to specify the concretegrammar for each operation and any corresponding input, output and faultmessage.

The definition of each service (with the corresponding ports) has thefollowing syntax:

<service name=myService>   <port name=myPort binding=myBinding>     ....  </port>   .... </service>

The attribute “name” of the service provides a unique name within theWSDL document (“myService”). For each port, the attribute “name”provides a unique name within the WSDL document (“myPort”); theattribute “binding” refers to the corresponding binding (“myBinding”).Extendibility elements are used to specify concrete network addresses ofone or more web servers (also called endpoints), which actuallyimplement the operations of the corresponding portType. If the servicehas multiple ports that share a portType, these ports provide asemantically equivalent behavior (but employing different bindings orendpoints).

Preferably, the definitions of the web services are separated intoindependent documents, which are included using corresponding elements(“import”). Moreover, an element “documentation” can be used in anydefinition for providing human readable information.

The WSDL is extended with specific binding elements for the most commonstandard protocols, such as the SOAP (Simple Object Access Protocol).The SOAP is a protocol that has been specifically designed for allowingprograms running in any kind of operating systems to communicate;particularly, one of the design goals of the SOAP is to encapsulateremote procedure calls (or RPCs).

The SOAP involves the exchange of messages between nodes; in detail, theSOAP messages travel from an initial sender node to an ultimate receivernode, possibly by passing through a set of intermediary nodes along thecorresponding path. Each SOAP message consists of an XML-based documentwith the following structure:

<env:Envelope xmls:env=myNamespace env:encodingStyle=myEncodingStyle>  <env:Header>   ....   </env:Header>   <env:Body>   ....   </env:Body></env:Envelope>

The SOAP message is enclosed in an envelope, which is defined by theelement “env:Envelope”. The attribute “xmls:env” allows specifying acorresponding namespace (“myNamespace”); moreover, the attribute“env:encodingStyle” is used to provide the URI (“myEncodingStyle”)qualifying the content of the SOAP message (according to correspondingrules that are used to serialize its content).

The envelope includes a header (defined by the element “env:Header”) anda body (defined by the element “env:Body”), typically organized intosub-elements (called blocks); the SOAP specification only determines howthese elements are handled, but not their contents (which areapplication dependent).

Particularly, the header is an optional element that can be used toprovide additional services, many of which involve the participation ofthe intermediary nodes. The blocks of the header are targeted at variousnodes that might be encountered along the message path; those nodes areidentified by their roles, which can be specified by an attribute“env:role”. Some standardized roles are defined in the SOAPspecification, such as “none” (meaning that no node should process theheader block), “next” (relating to the next node encountered in themessage path) or “ultimateReceiver” (for the receiver node). If theattribute “env:role” is missing, the header block is targeted at thereceiver node. The way in which each node assumes a particular role isnot part of the SOAP specification (but it is determined at theapplication level).

Each intermediary node receiving the SOAP message processes the headerblocks intended for its role (if possible) and then relays the SOAPmessage along the desired path. By default, the header blocks targetedat the intermediary node are removed from the outbound SOAP message(however, they may be reinserted, either unchanged or with theircontents altered, as a result of the processing). When a header blockmust be targeted at any capable intermediary node, an attribute“env:relay” with the value “true” is added; in this case, each headerblock targeted at the intermediary node is forwarded in the event thatit cannot be processed. An optional attribute “env:mustUnderstand” withthe value “true” can be inserted to indicate that the intermediary nodemust absolutely process the header blocks intended for its role in amanner consistent with their specification; on the contrary, the SOAPmessage is not relayed and a fault exception is thrown (as described inthe following). This feature ensures that the header blocks beingimportant to the overall purpose of the application would not beignored.

On the other hand, the body is a mandatory element that must beprocessed by the receiver node. Typically, in an RPC application thebody is used to invoke a procedure on the receiver node; for thispurpose, the body provides the identities and values of any inputparameters to be passed to the procedure. In response thereto, thereceiver node returns a SOAP message with a body providing theidentities and values of any output parameters. The SOAP for RPC offersa way to distinguish a return code of the procedure from the otheroutput parameters; the return code is identified by an element“rpc:result”, which contains the return code directly or a sub-element“m:status” (which in turn contains the actual return code).

The SOAP specification provides a model for handling situations whereinfaults arise in the processing of the SOAP message. For this purpose,all the faults are reported using a single element “env:Fault” in thebody of a SOAP message. The element “env:Fault” includes two mandatorysub-elements “env:Code” and “env:Reason”. The element “env:Code”consists of a mandatory sub-element “env:Value” (which provides astandardized identifier of the fault) and an optional sub-element“env:Subcode” (further qualifying the fault). The element “env:Reason”provides a human readable explanation of the fault. The element“env:Fault” can also include a sub-element “env:Node” for identifyingthe node that has generated the fault (its absence implies the fault hasbeen generated by the receiver node). A further optional sub-element“env:Role” specifies the role being played by the node that hasgenerated the fault.

The SOAP message must be bound to an underlying concrete transportprotocol. For each node along the message path, the transport protocolprovides a serialized representation of the SOAP message that can beconveyed to the next node (with each node that may support a differenttransport protocol). In addition, the transport protocol implementsdifferent features that are needed to the application. A particularfeature defines a message exchange pattern that is supported by thetransport protocol. For example, a request-response pattern provides theability to correlate a SOAP message acting as a request with a SOAPmessage acting as a response (which SOAP messages are exchanged betweentwo adjacent nodes); conversely, a response pattern consists of anon-SOAP request that is followed by a corresponding SOAP response. Thetransport protocol also offers a general feature, which allowsapplication full control over the choice of the actual method to becalled on the receiver node.

The SOAP specification supports the most common transport protocols,such as the HTTP. The HTTP provides a communication model wherein aclient identifies a server with a URI, connects to the server using theunderlying TCP/IP protocol, issues a HTTP request and receives a HTTPresponse over the same connection; the HTTP binding supports either therequest-response pattern (using the POST web method) or the responsepattern (using the GET web method). In this case, the request/responsefunctionality is provided in a native way (so that no further supportneeds be required at the application or SOAP level).

Referring back to the WSDL document, the binding for the SOAP protocolis signified by the following statement within the correspondingelement:

<soap:binding transport=mytransport style=myDefaultStyle>

The attribute “transport” indicates the corresponding transport protocol(“myTransport”, such as the HTTP); as described in the following, theattribute “style” specifies the default style for each containedoperation (“myDefaultStyle”).

The binding element then includes the concrete definition of eachoperation supported by the corresponding portType. Information for theoperation as a whole is provided by the following statement:

<operation soapAction=myAction style=myStyle>

The attribute “soapAction” specifies the actual action to be executedfor this operation (“myAction”); for example, in the HTTP binding theaction defines the header of the corresponding HTTP request. Theattribute “style” indicates whether the operation is RPC-oriented (i.e.,containing input/output parameters) or document-oriented (i.e.,containing one or more text documents). If the attribute “style” is notspecified, it defaults to the value indicated in the element“soap:binding”; if this element does not specify any style, it isassumed to be “document”. The value of the attribute “style” affects howthe information is assembled in the body of the SOAP message.Particularly, in a document-oriented operation the document is embeddedin the body directly; conversely, in an RPC-oriented operation eachparameter appears inside a wrapper, which is named identical to theparameter.

Each message is defined by the following statement:

<soap:body parts=myParts use=myUse encodingStyle=myEncodingStylenamespace=myNamespace/>

The optional attribute “parts” indicates the message parts that appearin the body (“myParts”); if this attribute is omitted, all the messageparts are assumed to be included in the body. The mandatory attribute“use” indicates a type of definition of the message (“myUse”); theattribute “use” has the value “literal” when the message defines aconcrete schema of the message, or the value “encoded” when the messagedefines an abstract specification that is serialized using some encodingrules. The attribute “encodingStyle” specifies the list of URIsidentifying the encoding rules (“myEncodingStyle”), from the mostrestrictive one to the least restrictive one. The attribute “namespace”provides the namespace that must be input to the encoding(“myNamespace”).

The binding also includes the definition of the header that can beinserted in the envelope:

<soap:header message=myMessage part=myPart use=myUseencodingStyle=myEncodingStyle namespace=myNamespace/>

The attributes “message” and “part” together reference the message partthat appears in the header; the attributes “use”, “encodingStyle” and“namespace” are exploited in the same way as with the element “body”. Anoptional element “headerfault” (having the same syntax of the element“header”) allows specifying the header that is used to transmitcorresponding error information.

The binding ends with the specification of the address of the relevantendpoint:

<soap:address location=myLocation/>

The attribute “location” provides the URI of the web server implementingthe endpoint (“myLocation”).

A more detailed description of the WSDL specification can be found inthe document “Web Services Description Language (WSDL) 1.1” and a moredetailed description of the SOAP specification can be found in thedocument “SOAP Version 1.2 Part 0:Primer”, both of them available at“http://www.w3.org/”.

As shown in FIG. 1 b, a generic computer of the above-describedinfrastructure (scheduling server, execution server, web server andregistry server) is formed by several units that are connected inparallel to a system bus 145. In detail, one or more microprocessors(μP) 150 control operation of the computer; a RAM 155 (typicallyconsisting of interleaved modules) is directly used as a shared workingmemory by the microprocessors 150, and a ROM 160 stores basic code for abootstrap of the computer. Peripheral units are clustered around a localbus 165 (by means of respective interfaces). Particularly, a mass memoryconsists of one or more hard-disks 170 and drivers 175 for readingCD-ROMs 180. Moreover, the computer includes input devices 185 (forexample, a keyboard and a mouse), and output devices 190 (for example, amonitor and a printer). A network Interface Card (NIC) 195 is used toconnect the computer to the INTERNET. A bridge unit 196 interfaces thesystem bus 145 with the local bus 165. Each microprocessor 150 and thebridge unit 196 can operate as master agents requesting an access to thesystem bus 145 for transmitting information. An arbiter 197 manages thegranting of the access with mutual exclusion to the system bus 145.

Similar considerations apply if the data processing infrastructure hasanother architecture or if each computer has an equivalent structure(for example, with different units). Moreover, the web services can bebound to other protocols (such as the HTTP GET & POST or the MIME), orthe SOAP messages can be conveyed in a different way (for example,within e-mails); more generally, the concepts of the present inventionare also applicable when the web services implement different functionsor are accessible according to equivalent interface documents (even ifdefined with a different language).

Moving to FIG. 2, the main software components that can be used topractice the method of the invention are depicted. The information(programs and data) is typically stored on the different hard-disks andloaded (at least partially) into the corresponding working memories whenthe programs are running, together with an operating system and otherapplication programs (not shown in the figure). The programs areinitially installed onto the hard disks from CD-ROMs.

Particularly, a central scheduling application controls the execution ofthe different jobs (typically during the evening); for example, the jobsconsist of payroll programs, cost analysis applications, and the like.The central scheduling application is composed of a job scheduler 205and one or more agents 210, which are installed on the correspondingservers.

The scheduler 205 includes a controller 215 for managing the submissionof the jobs. The controller 215 accesses a workload database 220 thatstores information about the different jobs. For each job, the workloaddatabase 220 includes a descriptor, a planned time of execution, anestimated duration, and any dependency from other jobs or resources ofthe system.

The descriptor identifies the agent 210 that is delegated to control theexecution of the job. In a standard scenario, each agent 210 executesone or more (local) jobs directly; in this case, the descriptor of eachlocal job specifies the corresponding steps (using a suitable controllanguage, such as the JCL). In addition or in alternative, the proposedsolution further supports the submission of (remote) jobs, which involvethe invocation of web services. In this case, the descriptor of eachremote job identifies the WSDL document pertaining to the correspondingweb service. The descriptor further specifies the name of the involvedservice (as defined in the WSDL document); moreover, the descriptoridentifies the port (in the service) and the operation (in the port).The descriptor then includes payload information defining a content ofthe message to be passed to the web service. Typically, the payloadinformation consists of a list of input parameters; some of the inputparameters can be symbolic variables to be resolved at run-time beforeinvoking the web service. Alternatively, the payload informationconsists of a simple document. In addition, the descriptor can includeauthentication information (such as userid and password), whichauthentication information is required by the web service to authorizeits invocation.

For example, the descriptor for a generic remote job has the followingformat:

agent = myAgent WSDLDocument = myWSDL userid= myUserid password =myPassword serviceNameSpace = myNameSpace serviceName = myServiceportName = myPort operationName = myOperation messageContent =  <myParameter>myValue</myParameter>   ....

The field “agent” provides a network address of the associated agent(“myAgent”) and the field “WSDLDocument” specifies the URI pointing tothe WSDL document (“myWSDL”). The fields “userid” and “password”identify the userid (“myUserid”) with its password (“myPassword”). Thefields “serviceNameSpace” and “serviceName” provide the namespace(“myNameSpace”) and the name (“myService”), respectively, of theinvolved service, and the fields “portName” and “operationName” specifythe port (“myPort”) and the operation (“myOperation”). The field“messagecontent” provides the payload information. Each input parameteris enclosed within a wrapper with an identical name (“myParameter”); theinput parameter consists of either a value or a symbolic variable (forexample, identified by a name starting with the symbol “$”).

The controller 215 transmits information about each job to be executed(stored in the workload database 220) to a builder 225. The builder 225creates one or more plans for controlling a flow of execution of batchesof jobs in a desired sequence (for example, covering a period of 24hours). Each plan is built according to several factors; typically, thefactors affecting the flow of execution include temporal values (such asdate, time, day of the week) and dependencies (such as completion ofpredecessor jobs or system resource availability). The plans are storedinto a corresponding repository 230. A selected plan from the repository230 is supplied, through the controller 215, to an executor 235. Theexecutor 235 submits the jobs of the plan; for this purpose, theexecutor 235 retrieves (from the workload database 220) and transits thedescriptor of each submitted job, denoted with 240, to the assignedagent 210.

Each agent 210 controls the execution of the corresponding jobs.Particularly, the steps of each local job are performed by the agent 210directly. Conversely, for each remote job the agent 210 retrieves theWSDL document of the corresponding web service (denoted with 245) fromthe URI specified in the descriptor 240. As explained in the following,the agent 210 builds a SOAP request 250, which is transmitted to the webservice to be invoked (denoted with 255). The web service 255 returns aSOAP response 260 to the agent 210 (if necessary). Once the execution ofa generic local or remote job terminates (because all the operationshave been completed or an error has occurred), the corresponding agent210 passes feedback information to the controller 215 (via the executor235); the feedback information includes an actual start time and anactual end time of the job, a return code specifying the result of theoperations, and any output data produced by the job. The controller 215uses this information to update the workload database 220 accordingly.

Similar considerations apply if the programs and the corresponding dataare structured in another way, if different modules or functions aresupported, or if the programs are provided on an equivalent computerreadable medium (such as a DVD). Alternatively, the jobs are associatedwith the corresponding descriptors in a different way (for example,using a lookup table), the workload database stores equivalentinformation, or the scheduler only passes a pointer to the descriptor ofeach submitted job to the corresponding agent. Moreover, the descriptorcan have a different structure (for example, consisting of one or moreseparate files), or the payload information can be provided in otherformats (such as with a list of type/value pairs, each one for acorresponding input parameter). In any case, the invention is alsosuitable to be used for scheduling submission of different jobs,interactive tasks, or more generally any other work units.

With reference now to FIGS. 3 a-3 c, a method 300 that is performed inthe above-described infrastructure begins at the black start circle 302in the swim-lane of the scheduler. Continuing to block 304, the desired(local and remote) jobs are defined in the workload database (enteringthe corresponding descriptor, the planned time of execution, and anydependency from other jobs or resources). The process passes to block306, wherein a new plan is created (or an existing plan is updated)specifying the flow of execution of the desired jobs. The plan can nowbe submitted for execution by the controller at block 308.

The flow of activities then includes two branches that are performedconcurrently. A first branch consists of blocks 310-318, and a secondbranch consists of blocks 320-326; the two branches joint at concentricwhite/black stop circles 328.

Considering in particular the branch 310-318, the executor at block 310identifies the jobs that are available for running (according to theirplanned time of execution and their dependencies). For each availablejob, the associated descriptor is retrieved from the workload databaseat block 312. Proceeding to block 314, the agent delegated to theexecution of the job is extracted from the descriptor. The method thenpasses to block 316, wherein the executor sends a request of executionof the job to the associated agent (which request of execution includesthe corresponding descriptor). The executor then verifies at block 318whether all the jobs of the plan have been submitted. If not, the flowof activities returns to block 310 for repeating the operationsdescribed above on the jobs of the plan still to be submitted.Conversely, the execution of the branch ends at the stop circles 328.

At the same time, in the other branch 320-326 the executor is in awaiting condition at block 320. As soon as a generic job terminates itsexecution, the corresponding feedback information is received from therespective agent at block 322. Continuing to block 323, the feedbackinformation is passed by the executor to the controller, and then loggedonto the workload database. Moreover, the controller at block 324updates the estimated duration of the job in the workload databaseaccordingly; for example, the estimated duration is calculated as arunning average of the values that have been measured for the completedinstances of the job (preferably filtering very different values asanomalies). A test is then made at block 326 to determine whether allthe jobs of the plan have been terminated. If not, the flow ofactivities returns to block 320 waiting for the completion of a furtherjob. Conversely, the execution of the branch ends at the stop circles328.

Moving now to the swim-lane of a generic agent, decision block 330 isentered in response to the request of execution of a job. The flow ofactivities then branches according to the type of job. Particularly, ifthe job is local the blocks 332-334 are executed, whereas if the job isremote the blocks 336-375 are executed; in both cases, the method thenjoints at block 376.

Considering now block 332 (local job), the steps of the job specified inthe descriptor are executed under the control of the agent directly. Assoon as the job completes, the return code of the job and the resultingoutput data are collected by the agent at block 334. The flow ofactivities then descends into block 376.

On the other hand, when the job is remote the agent at block 336downloads the WSDL document of the associated web service from the URIspecified in the descriptor. Proceeding to block 338, any symbolicvariable in the payload information of the descriptor is resolved intoan actual value. The payload information so obtained is then validatedat block 340; in other words, the agent verifies whether the payloadinformation is compliant with the corresponding definition provided inthe WSDL document. Assuming that the payload information is formallycorrect, a corresponding SOAP request is built at block 341 (accordingto the binding specified in the WSDL document). The SOAP request is thenembedded into a HTTP message at block 342.

The address of the endpoint implementing the desired operation isidentified at block 344 (as defined in the WSDL document). Continuing toblock 346, the agent opens a connection with the endpoint. In responsethereto, if the endpoint requires an authentication procedure (decisionblock 350), a corresponding request is returned to the agent. In thiscase, the agent at block 352 transmits the userid and the passwordprovided in the descriptor to the endpoint. Returning to the swim-laneof the endpoint, a test is made at block 354 to determine whether a useridentified by the information received from the agent is authorized toaccess the endpoint. If so, the access is granted at block 356;conversely, the access is denied at block 358. In both cases, the resultof the authentication procedure is returned to the agent at block 359.In response thereto, decision block 360 in the swim-lane of the agent isentered. If the access to the endpoint has been denied, the agent atblock 362 sets the return code of the job to an error value; the processthen descends into block 376 directly. Conversely, if the access to theendpoint has been granted the flow of activities continues to block 364;the same point is also reached from decision block 350 when the endpointdoes not require any authentication procedure.

Considering block 364, the SOAP request is transmitted to the endpoint.In response thereto, the endpoint at block 368 interprets the SOAPrequest and invokes the desired web service. Referring back to theswim-lane of the agent, the method branches at block 370 according tothe type of operation. If the WSDL specifies that the operation does notreturn any response, the return code of the job is set to a valueindicating its completion at block 371. Conversely, the agent enters awaiting condition at block 372. As soon as the endpoint returns the SOAPresponse (block 374), the agent at block 375 interprets the receivedmessage according to its definition in the WSDL document. Particularly,if the web service provides the expected output message the return codeof the job is set to the completion value; conversely, if the web serverprovides a fault message the return code of the job is set to the errorvalue. In both cases, the information extracted from the receivedmessage is dumped to a standard output of the job. The flow ofactivities then joints at block 376.

With reference now to block 376, the feedback information relating tothe execution of the job (i.e., the steps of the local job or theinvocation of the web service) is returned to the scheduler (see block322 in the corresponding swim-lane).

For example, let us consider the following WSDL document (stored at theURI “rateWSDL”):

<definitions name=rateName targetNamespace=rateNamespace <types>  <schema targetNamespace=rateSchema     <element name=”rateInput”>      <complexType>         <all>           <element name=”currency”        type=″string″/>         </all>       </complexType>    </element>     <element name=″rateOutput″>       <complexType>        <all>           <element name=”rate”           type=″float″/>        </all>       </complexType>     </element>   </schema> </types><message name=″getRateInput″>   <part name=″body″  element=″rateInput″/> </message> <message name=″getRateOutput″>  <part name=″body″   element=″rateOutput″/> </message> <portTypename=″ratePortType″>   <operation name=″getRate″>     <inputmessage=″getRateInput″/>     <output message=″getRateOutput″/>  </operation> </portType> <binding name=″rateBinding″type=″ratePortType″>   <soap:binding style=″document″  transport=”httt://schemas.xmlsoap.org.soap/http”/>   <operationname=″getRate″>     <soap:operation soapAction=myAction/>     <input>      <soap:body use=″literal″/>     </input>     <output>      <soap:body use=″literal″/>     </output>   </operation> </binding><service name=″rateService″>   <documentation>     Return the exchangerate of a desired currency   </documentation>   <port name=″ratePort″binding=″rateBinding″>     <soap:address location=”rateLocation″/>  </port> </service> </definitions>

The WSDL document (“rateName” at “rateNamespace”) defines a very simpleservice (“rateService”), which is provided by the endpoint at theaddress “rateLocation” using the SOAP over the HTTP. The service“rateService” includes the port “ratePort” with the binding“rateBinding”; the port “rateport” supports an operation “getRate”. Theoperation “getRate” receives a SOAP request (“getRateInput”) includingan input parameter “rateinput” of the string type, representing aselected currency, and returns an output parameter “rateOutput” of thefloat type, representing its exchange rate (both parameters conformingto the schema “rateSchema”).

Assuming that the above-described web service must be scheduled forexecution (such as every day), a corresponding job is defined in theworkload database. For example, the descriptor of the job includes thefollowing information:

agent = rateAgent WSDLDocument = rateWSDL userid= rateUserid password =ratePassword serviceNameSpace = rateNamespace serviceName = rateServiceportName = ratePort operationName = getRate messageContent =<rateInput>$VAR</rateInput>

In the example at issue, the input parameter “rateinput” is defined by asymbolic variable (“$VAR”), which is set to an identifier of the desiredcurrency every time the web service is invoked.

The job is scheduled for execution repeatedly, every time for adifferent currency. Whenever the remote job is submitted, the schedulersends the descriptor to the associated agent “rateAgent”. The agentresolves the symbolic variable “$VAR” into an actual value (for example,“USD”). The corresponding SOAP request is then built and embedded intothe following HTTP message:

POST Host: rateLocation Content-Type: text/xml; charset=″utf-8″Content-Length: .... SoapAction: myAction <CRLF> <env:Envelopexmls:env=”http://schemas.xmlsoap.org/soap/envelope/”>   <env:Body>    <m:getRateInput xmlns:m=rateNamespace>      <m:currency>USD</m:currency>     </m:getRateInput>   </env:Body></env:Envelope> <CRLF>

The agent then opens a HTTP connection with the endpoint “rateLocation”.In response to a corresponding request from the endpoint, the agentprovides the userid “rateUserid” and the corresponding password“ratePassword”. The above-described HTTP message is then transmitted.The WSDL document specifies that the Web Service must return a response;therefore, the agent waits for a HTTP message with the following format:

Content-Type: text/xml; charset=″utf-8″ Content-Length: .... <CRLF><env:Envelope xmls:env=”http://schemas.xmlsoap.org/soap/envelope/”>  <env:Body>     <m:getRateOutput xmlns:m=rateNamespace>      <m:rate>1.1875</m:rate>     </m:getRateOutput>   </env:Body></env:Envelope> <CRLF>

The SOAP response in the HTTP message indicates than no error occurred,and returns the value (1.1875) of the exchange rate for the desiredcurrency in the output parameter “rate”.

Similar considerations apply if an equivalent method is performed, or ifsome functions are executed by different modules. However, the conceptsof the present invention are also applicable when the web serviceimplements other types of operations, when the agent is validated with adifferent procedure (for example, involving the use of a digitalcertificate), and the like.

More generally, the present invention proposes a method of schedulingexecution of work units in a data processing infrastructure with adistributed architecture. The method includes a series of steps, whichare performed under the control of a central scheduling application. Themethod starts associating one or more work units with a descriptor; thedescriptor includes an indication of an external service that isaccessible according to a predefined interface document. The work unitsare then submitted for execution according to a predefined plan. Themethod continues retrieving the interface document of each externalservice associated with the submitted work units. A request message isthen built for each external service associated with the submitted workunits according to the corresponding interface document. The method endssending each request message to the corresponding external service, inorder to cause the invocation of the external service.

The proposed solution enables the scheduler to manage external services.

Particularly, this allows the scheduler to invoke the external servicesin a very simple manner.

Therefore, the method of the invention is well suited to be used inheterogeneous environments.

The devised technique supports the integration of the scheduler with theexternal services.

In this way, the additional functions already available in the schedulercan be readily exploited for managing the external services. Forexample, it is possible to handle temporal and predecessor constraints,to control and monitor the operations performed by the scheduler throughits GUI, or to exploit performance monitoring, load balancing andreporting functions (even if the use with schedulers providing otherfunctions is not excluded).

The preferred embodiment of the invention described above offers furtheradvantages.

Particularly, the web server returns a response message to the agent(which response message is interpreted according to its definition inthe corresponding WSDL document).

In this way, a complete communication loop is closed between thescheduler and the web servers.

Advantageously, the content of the request message is included in thedescriptor and it is then embedded into the corresponding structurespecified in the associated WSDL document.

The proposed technique is very simple, but at the same time effective.

As a further enhancement, the content of the request message includesone or more symbolic variables, which are resolved into actual values atrun-time.

This feature increases the flexibility to the method (for example,allowing the same web service to be invoked repeatedly with differentinput parameters).

However, the solution according to the present invention leads itself tobe implemented even with web services that do not return any responsemessage. Alternatively, the request message is built in a different way;for example, in another embodiment of the invention the descriptorstores the actual request message directly (which is simply retrieved bythe agent and sent to the corresponding web service). Moreover, thesymbolic variables can be resolved by the scheduler, or the content ofthe request message stored in the descriptor can only consist of staticinput parameters.

In a preferred implementation of the invention, the submission of thejobs is controlled by the scheduler and their actual execution iscontrolled by one or more agents.

The proposed architecture makes it possible to exploit pre-existingschedulers (simply defining specific jobs in the workload database forthe invocation of the web services). The task of controlling theinteraction with the web services is instead entrusted to the agents,which can be simply plugged into a standard infrastructure.

A suggested choice for associating each remote job with the WSDLdocument of the corresponding web server consists of storing its addressinto the respective descriptor.

This feature ensures that the agents always access the up-to-dateversion of the desired WSDL documents.

A way to further improve the solution is to include authenticationinformation into the descriptor, which authentication information isthen used by the web server to authorize its invocation by the agent.

In this way, the scheduling of the web services can be completelyautomated without any security concern.

Without detracting from its general applicability, the method of theinvention is specifically designed for invoking web services.

Indeed, the devised solution is an important step in the move todistributed computing on the INTERNET. Particularly, the method of theinvention facilitates the full exploitation of the INTERNET (forexample, allowing the interoperability of legacy applications with webservices provided by third parties).

However, the solution according to the present invention is alsosuitable to be implemented with scheduling applications having adifferent architecture (for example, wherein the whole processing logicis embedded into the scheduler). Alternatively, copies of the WSDLdocuments are stored locally (and the corresponding addresses arespecified in the descriptors), or the WSDL documents are embedded intothe descriptors directly; for example, this approach can be useful whenthe WSDL documents of some web services are not published in theINTERNET. In any case, the proposed method is also applicable todifferent standardized services (such as the ones conforming to the EDIspecification), or more generally to the scheduling of any externalservices.

Advantageously, the solution according to the present invention isimplemented with a computer program, which is provided as acorresponding product embodied in a suitable medium.

Alternatively, the program is pre-loaded onto the hard-disks, is sent tothe computers through the INTERNET, is broadcast, or more generally isprovided in any other form directly loadable into the working memoriesof the computers. However, the method according to the present inventionleads itself to be carried out with a hardware structure (for example,integrated in chips of semiconductor material), or with a combination ofsoftware and hardware.

Naturally, in order to satisfy local and specific requirements, a personskilled in the art may apply to the solution described above manymodifications and alterations all of which, however, are included withinthe scope of protection of the invention as defined by the followingclaims

1-12. (canceled)
 13. A system, comprising: a scheduler; a set of agents;a processor; and a memory coupled to the processor, wherein the memorycomprises instructions which, when executed by the processor, cause theprocessor to: submit, by the scheduler, a set of work units forexecution according to a predefined plan, wherein the scheduler and theset of agents are comprised in a central scheduling application; foreach work unit in the set of work units, identify, by the scheduler adescriptor associated with each work unit, wherein the descriptoridentifies an external service within a set of external services that isto execute the work unit and wherein the descriptor further comprises anindication of an agent in the set of agents that is associated with thework unit; send, by the scheduler, a request of execution of the workunit to the agent, wherein the request of execution comprises anindication of the descriptor; retrieve, by the agent, an interfacedocument of the external service; build, by the agent, a request messagefor the work unit according to the interface document; and send, by theagent, the request message to the external service to cause invocationof the external service in response to the request of execution.
 14. Thesystem according to claim 13, wherein the instructions further cause theprocessor to: receive a response message from the external service beinginvoked; and interpret the response message according to the interfacedocument.
 15. The system according to claim 13, wherein the interfacedocument specifies a structure of the request message, wherein thedescriptor further comprises an indication of a content of the requestmessage, and wherein the instructions to build the request messagefurther cause the processor to: embed the content of the request messageinto the structure of the request message.
 16. The system according toclaim 15, wherein the indication of the content of the request messagecomprises a set of input parameters to be passed to the externalservice, wherein at least one input parameter of the set of inputparameters is a symbolic variable, and wherein the instructions to buildthe request message further cause the processor to: resolve the symbolicvariable into an actual value.
 17. The system according to claim 13,wherein the descriptor identifies an address of an external location inthe external service where the interface document is stored and whereinthe instructions to retrieve the interface document further cause theprocessor to: download the interface document from the externallocation.
 18. A computer program product stored on a computer readablemedium having a computer readable program, wherein the computer readableprogram, when executed in a data processing system, causes the dataprocessing system to: submit, by a scheduler, a set of work units forexecution according to a predefined plan, wherein the scheduler and aset of agents are comprised in a central scheduling application; foreach work unit in the set of work units, identify, by the scheduler, adescriptor associated with each work unit, wherein the descriptoridentifies an external service within a set of external services that isto execute the work unit and wherein the descriptor further comprises anindication of an agent in the set of agents that is associated with thework unit; send, by the scheduler, a request of execution of the workunit to the agent, wherein the request of execution comprises anindication of the descriptor; retrieve, by the agent, an interfacedocument of the external service; build, by the agent, a request messagefor the work unit according to the interface document; and send, by theagent, the request message to the external service to cause invocationof the external service in response to the request of execution.
 19. Thecomputer program product according to claim 18, wherein the computerreadable program further causes the data processing system to: receive aresponse message from the external service being invoked; and interpretthe response message according to the interface document.
 20. Thecomputer program product according to claim 18, wherein the interfacedocument specifies a structure of the request message, wherein thedescriptor further comprises an indication of a content of the requestmessage, and wherein the computer readable program to build the requestmessage further includes computer readable program that causes the dataprocessing system to: embed the content of the request message into thestructure of the request message.
 21. The computer program productaccording to claim 20, wherein the indication of the content of therequest message comprises a set of input parameters to be passed to theexternal service, wherein at least one input parameter of the set ofinput parameters is a symbolic variable, and wherein the computerreadable program to build the request message further includes computerreadable program that causes the data processing system to: resolve thesymbolic variable into an actual value.
 22. The computer program productaccording to claim 18, wherein the descriptor identifies an address ofan external location in the external service where the interfacedocument is stored and wherein the computer readable program to retrievethe interface document further includes computer readable program thatcauses the data processing system to: download the interface documentfrom the external location.